Various methods are known for adhering multiple sheets of materials together to form a thicker product, the properties of which differ from the individual sheets. Lamination processes of this type are used widely to adhere or bond thin sheets of flexible foam to a sheet of cover material and, in many instances, to a piece of backing material. The foam laminate is cut to the desired shape with a cutting machine. For example, a foamed article may be die cut from a laminate sheet by the impact of a die against the sheet. Hot wire cutting may also be used in some applications. These soft foam articles are then used for a number of purposes such as seat cushions, back cushions, and the like.
A variety of foams, cover materials and backings are available for use in producing shaped foam articles. The most widely used foam is polyurethane. Polyurethane is a polymer which is produced by the condensation of a polyisocyanate and a hydroxyl-containing material, usually a polyol. In order to "foam" the polyurethane to form a polyurethane foam, a blowing reaction is induced using a blowing agent. The blowing agent may comprise one or more substances which vaporize during the reaction of the polyisocyanate and the polyol such as a flurocarbon, or the blowing agent may react chemically with the isocyanate to produce a gas such as the reaction of water with isocyanate which liberates carbon dioxide. Foam softness is in part a function of the foam density with lower density imparting greater softness. One excellent polyurethane foam for use in forming foam articles is polyether polyurethane foam often referred to simply as polyether foam. Polyether serves as the polyol in the production of polyether polyurethane foam. Urethane foams can be rigid or flexible and can be made in virtually any desired thickness.
Many materials suitable for use as cover material or "body cloth" in forming a laminated foam article are also known, including both synthetic and natural fabrics, blown or cast films, or animal skins and the like. The choice of body cloth fabric or material is dictated by the end use of the laminate product. Similarly, a backing scrim which is applied to the foamed article on the foam surface opposite that to which the body cloth is adhered may be any of a number of suitable materials.
As will be appreciated by those skilled in the art, it is often necessary or desirable to emboss or impress a pattern upon a laminated foam article for decorative purposes. An embossed design on laminated foam articles is customarily used for seat and back cushions in the manufacture of motor vehicles. Several methods of producing an embossed design are known. Prior art methods include sewing or stitching the laminate such that the desired pattern is formed as the stitches compress regions of the resilient foam. That is, the laminate is sewn so that the foam is compressed along the stitching in a predetermined pattern. An embossed effect is thereby achieved since the foam which is spaced laterally from the area compressed by the stitches is raised relative to the stitching lines.
Another method for achieving an embossed or relief design is described in U.S. Pat. No. 4,400,422. There, a laminate comprising a cover layer of cloth or vinyl material, a backing material or scrim and a layer of foam interposed between the cover and scrim is processed to form intermittent raised areas. A solid object or insert in the shape of a button or the like is preferably inserted between the cover material and the foam layer. Prior to laminating the three layers, both surfaces of the foam are coated with anhydrous polyurethane foam-forming materials. The cover layer and backing are then placed in contact with the coated foam layer and moisture is introduced into the cover and backing material. The button form or the like is then inserted between the cover material and the foam layer and a heated press forces the layers against a die. Water is driven from the backing material into the anhydrous foam-forming materials whereby foaming of the anhydrous polyurethane begins.
As the foaming material expands, it penetrates the interstices of the cover material and the foam layer. In other words, as the water-activated anhydrous polyurethane begins to foam, it expands into the cover material interstices and, simultaneously, into the foam layer at the interface of the two layers. Thus, a bond is formed which secures the cover layer to the foam layer. The same process binds the scrim to the opposite side of the foam layer. In addition, the die protrusions force the two foaming regions at opposite sides of the foam layer together such that the foaming regions bond to one another. The bonding together of these two foaming regions compresses the foam layer along the lines of the die projections, in essence, bonding the cover material to the backing material. The compression of the foam layer at this bond causes a depression or embossed effect surrounding the button form insert. It is disclosed that additional embossed decorative patterns in the fabric can be formed in this manner without the use of a structural form. However, this method may only be used with relatively thin pieces of foam and produces stiff or rigid embossed lines. Moreover, this method requires that the lamination of the cover material and backing to the foam take place simultaneously with the formation of the embossed design which may be impractical in many applications. Also, in order to achieve substantial penetration of the foam layer interstices by the foaming materials, it is necessary to use a low density foam layer.
Thus it would be desirable to provide a method for making a laminated foam article having an embossed design which does not require intricate stitching of the laminate or complicated foaming processes. It would further be desirable to provide such a method which does not require that the embossing step be undertaken simultaneously with the bonding together of the layers which comprise the laminate. It would still further be desirable to provide such a method by which relatively thick foam layers can be easily embossed and which produces a pliable yet permanent decorative embossed line. The present invention provides such a method for forming an embossed laminated foam article.